Systems and methods for power distribution in a drone aircraft

ABSTRACT

Systems and methods for power distribution in a hybrid fixed-wing VTOL drone aircraft are disclosed. In an embodiment, a drone aircraft is capable of two modes of operation. In a first mode of operation, the internal combustion engine is shut off while an electric motor-based VTOL system provides lift and thrust. In a second mode of operation, an internal combustion engine provides thrust while a set of fixed wings provide lift. In the second mode of operation, mechanical power from the internal combustion engine provides for power generation to charge an electrical battery to power the electric motor-based VTOL system.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication No. 62/687,249, filed Jun. 20, 2018, which is herebyincorporated by reference in its entirety.

FIELD

The present disclosure relates to drone delivery systems, and morespecifically to for power distribution for hybrid fixed-wing VTOL droneaircraft.

BACKGROUND

Drone aircraft are typically one of two types. A first type is afixed-wing design, where lift is provided by one or more fixed wings andforward thrust is provided by a spinning propeller, ducted fan, or jetengine. A second type is a helicopter-type design where lift and forwardthrust are provided by one or more vertically oriented rotors or rotarywings. Included in this second type is the so-called ‘quad-copter’design which incorporates four vertical rotors. Manipulation of therelative thrust provided by each of the four rotors provides forvariable vertical thrust and forward and lateral movement. Fixed-wingaircraft of the first type are generally efficient in long distancetransportation. The various multicopter designs of the second type aregenerally less efficient but have the unique ability to take offvertically. These aircraft designs are said to be capable of VerticalTake-Off and Landing, or VTOL.

Aircraft may use various types of power for thrust and propulsion aswell. One type of thrust or propulsion is electric thrust powered bybattery power. Electric power may be easy to control by solid stateelectronics, but battery power storage density is relatively low, suchthat battery weight is often a significant concern in designing anaircraft. Furthermore, a fully-charged battery weighs approximately thesame as a depleted battery. Fossil fuel burning internal combustionengines may also be used in drone aircraft. Liquid fuel provides severaladvantages. First, it is very energy dense, so an internal combustionengine may produce significant lift or thrust from a given amount offuel. Second, is that the weight of fuel decreases as it is consumed,such that a plane becomes lighter as it flies.

SUMMARY

Described herein are hybrid fixed-wing VTOL drone aircraft with onboardcharging of electrical propulsion systems. Embodiments disclosed relateto a drone aircraft design which incorporates VTOL capabilities withfixed-wing efficiencies. These drone aircraft may take-off and landunder electric power in a VTOL configuration, and cruise in-betweenunder gas powered thrust and fixed-wing lift. Drone aircraft accordingto various embodiments may travel hundreds of miles using this hybridpropulsion system, making multiple take-off and landing stops on theway. Such drone aircraft may be useful for drone-based delivery systems,for example.

One challenge of the hybrid design is to keep overall weight down.Embodiments disclosed herein use comparatively small chemical batteriesto provide electric power for VTOL operations, and liquid fuel tanks forgas powered fixed-wing operation. The chemical batteries need only besized to sustain limited VTOL operation, as they may be recharged fromthe gas engine in-flight. In this way, the best qualities andcapabilities of different thrust and lift systems as well as powersystems are combined. These drones then may be capable of multiple VTOLtake-offs and landings with a comparatively small battery capacity,decreasing overall weight and efficiency of the drone aircraft.

Further areas of applicability of the present disclosure will becomeapparent from the detailed description, the claims and the drawings. Thedetailed description and specific examples are intended for purposes ofillustration only and are not intended to limit the scope of thedisclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will become more fully understood from thedetailed description and the accompanying drawings, wherein:

FIG. 1 illustrates a block diagram of an avionics system according to anembodiment;

FIG. 2 illustrates a power supply architecture according to anembodiment; and

FIG. 3 illustrates a redundant servo power supply architecture accordingto an embodiment.

In the drawings, reference numbers may be reused to identify similarand/or identical elements

DETAILED DESCRIPTION

Some types of drones, or Unmanned Aerial Vehicles (UAV), may use acombination of fixed wings and rotors to provide for Vertical Take-Offand Landing (VTOL) and high-speed cruising. In some hybrid-fixed wingdrones, the VTOL rotors may be powered by electric motors, and forwardthrust provided by a gas engine. But in some known drones, the batterycapacity that powers the VTOL propulsion system may be limited becausebatteries are comparatively heavy. Thus, these drone systems may belimited in their hover time which limits the number of take-offs andlandings possible on a single charge.

In the following description, for purposes of explanation, specificdetails are set forth in order to provide an understanding of theinvention. It will be apparent, however, to one skilled in the art thatthe invention can be practiced without these details. Furthermore, oneskilled in the art will recognize that embodiments of the presentinvention, described below, may be implemented in a variety of ways,such as a process, an apparatus, a system, a device, or a method on atangible computer-readable medium.

Components, or modules, shown in diagrams are illustrative ofembodiments of the invention. It shall also be understood thatthroughout this disclosure that components may be described as separatefunctional units, which may comprise sub-units, but those skilled in theart will recognize that various components, or portions thereof, may bedivided into separate components or may be integrated together,including integrated within a single system or component. It should benoted that functions or operations discussed herein may be implementedas components. Components may be implemented in software, hardware, or acombination thereof.

Furthermore, connections between components or systems within thefigures are not intended to be limited to direct connections. Rather,data between these components may be modified, re-formatted, orotherwise changed by intermediary components. Also, additional or fewerconnections may be used. It shall also be noted that the terms“coupled,” “mechanically coupled,” “connected,” or “electricallyconnected” shall be understood to include direct connections, indirectconnections through one or more intermediary devices, and wirelessconnections.

Reference in the specification to “one embodiment,” “an embodiment,”“some embodiments,” or “embodiments” means that a particular feature,structure, characteristic, or function described in connection with theembodiment is included in at least one embodiment of the invention andmay be included more than one embodiment. Also, the appearances of theabove-noted phrases in various places in the specification are notnecessarily all referring to the same embodiment or embodiments.

The use of certain terms in various places in the specification is forillustration and should not be construed as limiting. A service,function, or resource is not limited to a single service, function, orresource; usage of these terms may refer to a grouping of relatedservices, functions, or resources, which may be distributed oraggregated. Furthermore, the use of memory, database, information base,data store, tables, hardware, and the like may be used herein to referto system component or components into which information may be enteredor otherwise recorded.

Furthermore, it shall be noted that: (1) certain steps may optionally beperformed; (2) steps may not be limited to the specific order set forthherein; (3) certain steps may be performed in different orders; and (4)certain steps may be done concurrently.

FIG. 1 illustrates a block diagram of an avionics system according to anembodiment. The avionics system illustrates in FIG. 1 may be a componentof a hybrid VTOL drone aircraft, for example. Avionics board 101 may bea computing platform for piloting a semi-autonomous or autonomous droneaircraft. Avionics board 101 may interface with of peripheral devices102, including, for example, CPUs, autopilot modules, GPS sensors,inertial sensors, LIDAR systems, air speed sensors, magnetometers,barometers, gyroscopes, radio interfaces, lights, payloads, or othersuch sensors or systems. Peripheral devices 102 may include one or moreradio systems such as a 900 MHz radio, cellular LTE or Wi-Fi radio, or asatellite radio system such as an IRIDIUM satellite communicationssystem. Peripheral devices 102 may also include an emergency parachutethat is to be deployed in the event of the loss of loss of flight tosave an aircraft from crashing.

In some embodiments, avionics board 101 may include a plurality ofcommunications systems. For example, in an embodiment, avionics board101 includes a 900 MHz or 2.4 GHz radio, a cellular LTE radio, and asatellite radio system. In this example, all three radio communicationssystems may be used concurrently for various telemetry and/or commandand control purposes. In some embodiments, the plurality ofcommunications systems may be used in a cascading failover configurationto provide redundancy and robust communications capabilities to theavionics system.

In some embodiments, avionics board 101 may be integrated with one ormore of peripheral devices 102 in a single package or housing. In someembodiments, avionics board 101 may be an autopilot implemented on acomputing platform specially designed for a drone aircraft. For example,in an embodiment, avionics board 101 may be a PIXHAWK® brandauto-pilot-on-module system. In another embodiment, avionics board 101may be a PICCOLO™ brand autopilot module. Avionics board 101 mayinterface with one or more servo motors 103 which actuate controlsurfaces of the drone aircraft. For example, servo motors 103 mayactuate rudders, alerions, flaps, elevators, thrust vectoring devices,rotor orientation, collective pitch, or other such drone aircraftcontrol surfaces.

VTOL propulsion 108 may be, for example, a set of rotors oriented toprovide vertical thrust for a drone aircraft. For example, one or moreelectric motors may drive one or more rotors to provide vertical thrust.VTOL propulsion 108 may include one or more speed controllers thatmodulate the thrust provided. VTOL propulsion 108 draws electrical powerfrom VTOL battery 107. VTOL battery 107 may be, for example, alithium-ion type battery system, or a similar such chemical battery.VTOL battery 107 may be, for example a battery pack consisting ofseveral individual battery cells wired in series. For example, VTOLbattery 107 may be comprised of 14 cells wired in series, sometimesreferred to as a ‘14S’ configuration. VTOL battery 107 is charged byVTOL charger 106. VTOL charger 106 monitors the battery charge andhealth of VTOL battery 107 and charges VTOL battery 107 when necessary.VTOL battery 107 may be switched on or off by avionics board 101 and mayalso be variably controlled by avionics board 101.

Gas motor 111 may drive one or more propellers to provide forward thrustfor a drone aircraft. Gas motor 111 may operate on gas combustion of aliquid fuel, for example. Starter/alternator 110 is mechanically coupledto gas motor 111 such that starter/alternator 110 is mechanically drivenby the operation of gas motor 111. Starter/alternator 110 has twofunctions. First, it may operate as an electric motor to provide aninitial mechanical energy to start gas motor 111 from a resting state.Second, starter/alternator 110 may be mechanically driven by gas motor111 to generate an electrical current.

Additional sources of electrical power may be included in someembodiments. Some embodiments may include fuel cell system 112,photovoltaic module 113, or both fuel cell system 112 and photovoltaicmodule 113. In addition, some embodiments may not include either fuelcell system 112 or photovoltaic module 113. These additional electricalpower sources may provide electrical power to any avionics systemcomponent, including other electrical power storage components. Forexample, various battery systems may be charged by these additionalelectrical power sources. In other embodiments, other electrical powersources may also be used.

In an example, fuel cell system 112 provides additional electrical powerthat may be used by various components. For example, fuel cell system112 may provide electrical power to charge VTOL battery 107 or any otherbattery system. In some embodiments, fuel cell system 112 includes aplurality of fuel cell devices and accompanying regulation andmanagement circuitry.

In another example, photovoltaic module 113 may similarly provideelectrical energy to the avionics system. Photovoltaic module 113 may becomprised of a plurality of photovoltaic cells in any arrangement aswell as accompanying regulation and management circuitry. For example,photovoltaic module 113 may provide electrical power to charge VTOLbattery 107 or any other battery system.

Power Management Unit (PMU) 109 acts as a power regulator to route powerthroughout the avionics system in conjunction with gas power board 105.Gas power board 105 serves to route the various power lines betweenavionics board 101, VTOL charger 106, PMU 109, PMU battery 104, optionalfuel cell system 112, and optional photovoltaic module 113.

In a first state, when gas motor 111 is at a high speed,starter/alternator 110 receives mechanical power from gas motor 111 andprovides electrical power to PMU 109. This first state may correspond tothe drone aircraft flying primarily under power of gas motor 111, usingfixed wings for lift. In this state, PMU 109 receives power fromstarter/alternator 110 and provides three regulated power outputs. Afirst regulated power output is for charging VTOL battery 107. In anembodiment, this first regulated power output may be approximately 24Vand capable of providing approximately 350 W of power to charge VTOLbattery 107. PMU 109 also provides for a second and third regulatedpower output for powering avionics board 101. In an embodiment, a secondregulated power output of PMU 109 may be approximately 15V and capableof providing approximately 108 W of power to avionics board 101. In anembodiment, a third regulated power output of PMU 109 may beapproximately 8V and capable of providing approximately 42 W of power toavionics board 101.

In a second state, gas motor 111 is at a low speed or in an off state.This second state may correspond to, for example, a condition where adrone aircraft is under power of VTOL propulsion 108, for example duringa take-off or landing event. In this second state, PMU 108 receiveselectrical power from PMU battery 104. Using the same regulators andpower management, PMU is then able to provide the second and thirdregulated power output to avionics board 101. In this second state, VTOLcharger 106 is disconnected, such that it does not draw power from PMUbattery 104. In a transition from the second state to the first state,starter/alternator 110 draws electrical power from PMU battery 104 tomechanically start gas motor 111. After gas motor 111 is started,starter/alternator 110 may draw mechanical power from gas motor 110 toprovide electrical power to PMU 109 as described above.

In some embodiments, one or more of the components illustrated in FIG. 1may be integrated into one housing or assembly. For example, in anembodiment, PMU 109, gas power board 105, and VTOL charger 106 may beintegral to each other. In some embodiments, these components may befurther integrated with avionics board 101. Any other combination ofcomponents or subcomponents may be similarly employed in variousembodiments.

FIG. 2 illustrates a power supply architecture of an avionics boardaccording to an embodiment. Specifically, FIG. 2 illustrates a powerdistribution architecture for components of an avionics board such asavionics board 101, including peripheral devices such as peripheraldevices 102. A loss of power to any major flight system may result inthe loss of aircraft power, and ultimately the cargo it may be carrying.In an embodiment, an avionics board includes redundant power supply toensure mission success. In some embodiments, most systems of an avionicsboard operate on 5V power. Two 5V power regulators 201 and 202 providefor redundant power regulation for these components. In an embodiment,each 5V power regulator is driven from a different power supply. Forexample, 5V primary 201 may receive input power from a 15V output from aPMU and 5V backup 202 receive input power from an 8V power output from aPMU. Power Selection Unit (PSU) 203 selects which 5V regulator toreceive power from. PSU 203 monitors the output from 5V primary 201 and5V backup 202 and switches power lines if the voltage drops out of anacceptable range. For example, if power is being drawing from 5V primary201 and PSU 203 detects that the voltage has dropped below somethreshold, for example 10%, then PSU 203 disconnects 5V primary 201 andswitches to 5V backup 202. In this way, a complete failure of one of thesources of 5V power for the flight critical electronics will not cause aloss of the vehicle.

The power distribution within the avionics board is designed forreliability and robustness. In an embodiment, the various peripheralcomponents of an avionics board are split into two group. Examples ofperipherals include but are not limited to, radios, GPS devices,communication bus deices, LIDAR devices, and other such peripherals.Each group, peripheral set #1 207 and peripheral set #2 208 are drivenby independent current limited rails 204 and 205. 5V current limitedrail #1 and 5V current limited rail #2 may be implemented by, forexample, voltage regulator circuits or fuse circuits. Due to thisarchitecture, if any one peripheral device fails and produces a shortacross the 5V power supply, only those devices on the same currentlimited rail will be affected. In other embodiments, fewer or morecurrent limited rails may be used. For example, one embodiment includesthree current limited rails. In an embodiment, a CPU or autopilot 206may be on its own current limited rail or directly connected to the 5Vsupply from PSU 203.

FIG. 3 illustrates a redundant servo power supply architecture accordingto an embodiment. Specifically, FIG. 3 illustrates a power distributionarchitecture for one or more servo motors such as servo motors 103.Servo motors also draw power from redundant power supplies. Servo powerrail 304 provides power to one or more servo motors that control variouscontrol surfaces of a drone aircraft. 8V primary servo power regulator301 may receive power from an output of a PMU such as a 15V output. 8Vsecondary servo power regulator 302 may receive power from a differentoutput of a PMU such as an 8V output. A PMU may supply this secondary 8Voutput from either an alternator input or a separate battery such as a,8.4V avionics battery. Current monitoring logic 303 monitors the outputfrom both 8V primary servo power regulator 301 and 8V secondary servopower regulator 302 and switches power lines if the voltage drops out ofan acceptable range. In some embodiments, servo power rail 304 mayexperience high surge current due to the operation of servo motors, soboth 8V primary servo power regulator 301 and 8V secondary servo powerregulator 302 may be capable of up to, for example 25A surge currents.

Other various components or peripherals of an avionics board such asavionics board 101 may be powered by other redundant power supplysystems. For example, a separate power regulator may be included in anavionics board for navigation lights. As an example, FAA-mandatednavigation lights may consume large amounts of power in a sporadic,transient manner. To prevent these transient fluctuations from affectingother components (including flight critical components), there is aseparate power regulator for just the navigation lights. This separateregulator may be, for example a 5V regulator and receive power from a15V output of a PMU or a battery system.

Other components or subsystems that may be powered by separate regulatedpower supplies may include, for example, a power supply for acommunications radio, or a magnetic payload gripper. In variousembodiments, any system-critical component or component that may consumelarge amounts of transient power may be powered by an independent powersupply within an avionics board. In this way, overall system reliabilitymay be increased by isolating power-consuming devices and preventing anyone component from disabling other components in the event of a failure.

In addition, various subsystems or power delivery components may be ableto be isolated by mechanical switches for safety reasons during testingand repair. In an embodiment, power for an aircraft is grouped into foursystems: avionics, propulsion, VTOL propulsion, and payload. Power toeach system may be independently turned off via a mechanical switch oron-board logic. An operator may choose to enable or disable anyindividual system via the position of toggle switches. These switchesare intended to be used by technicians and operators during testing andtroubleshooting. They are not intended for general use in operation. Inaddition, a general, system-wide switch may be included in someembodiments to fully power down all systems of a drone aircraft forsimilar purposes. For example, all power systems may be disconnected forstorage or maintenance purposes. In some embodiments, an emergency offswitch may be included that also disconnects all power systems of adrone aircraft. Such an emergency off switch may be used during testingor maintenance for emergency purposes only.

The foregoing description is merely illustrative in nature and is in noway intended to limit the disclosure, its application, or uses. Thebroad teachings of the disclosure can be implemented in a variety offorms. Therefore, while this disclosure includes particular examples,the true scope of the disclosure should not be so limited since othermodifications will become apparent upon a study of the drawings, thespecification, and the following claims.

What is claimed is:
 1. A power distribution system for a drone aircraft,comprising: a power management unit, installed in a drone aircraft; anelectric battery system electrically connected to the power managementunit wherein the electric battery system comprises at least one electricbattery; an electric propulsion system, configured to produce verticalthrust, electrically connected to the electric battery system, whereinthe drone aircraft performs Vertical Take-Off and Landing (VTOL) underpower of the electric propulsion system and wherein the batteries are ofa combined capacity to power the electric VTOL propulsion system for asingle take-off or landing; an internal combustion propulsion system,separate from the electric propulsion system, configured to produceforward thrust, independent of the electric propulsion system; and anelectric generator mechanically coupled to the internal combustionpropulsion system and electrically connected to the power managementunit through a mechanical switch configured to selectively disconnectthe power management unit from the electric generator; wherein the droneaircraft comprises one or more fixed wings, wherein, in horizontalflight, the internal combustion propulsion system produces the forwardthrust and the one or more fixed wings produce lift, wherein, inhorizontal flight, the mechanical switch is in a closed position,connecting the electric generator to the power management unit, wherein,in horizontal flight, the internal combustion propulsion system isfurther configured to charge the at least one electric battery bymechanically driving the electric generator, wherein, in VTOL flight,the mechanical switch is actuated into an open position, isolating theelectric generator and the internal combustion propulsion system fromthe power management unit and the electric battery system.
 2. The systemof claim 1, wherein the electric propulsion system comprises one or moreelectric motors mechanically coupled to one or more rotary wingsconfigured to generate lift.
 3. The system of claim 1, furthercomprising a starter motor mechanically coupled to the internalcombustion propulsion system and electrically connected to the powermanagement unit, wherein the power management unit is configured to drawpower from the electric battery system to power the starter motor toinitiate operation of the internal combustion propulsion system whentransitioning from VTOL flight to horizontal flight.
 4. The system ofclaim 1, wherein the electric battery system comprises two or moreelectric batteries.
 5. A hybrid fixed-wing Vertical Take-Off and Landing(VTOL) drone aircraft, comprising: an electric VTOL propulsion system,configured to produce vertical thrust; an internal combustion propulsionsystem, independent of the electric VTOL propulsion system, configuredto produce horizontal thrust; an electric battery of sufficient capacityto power the electric VTOL propulsion system for a single take-off orlanding; an electric generator mechanically coupled to the internalcombustion propulsion system and electrically connected, through amechanical switch, to the electric battery, wherein the electricgenerator is configured to selectively charge the electric battery,wherein the mechanical switch is configured to be actuated into an openposition, disconnect the electric battery from the electric generator,during take-offs and landings, and wherein the drone aircraft performsmultiple take-offs and landings under power of the electric VTOLpropulsion system by charging the electric battery from the electricgenerator in between take-offs and landings.
 6. The hybrid fixed-wingVTOL drone aircraft of claim 5, wherein the internal combustionpropulsion system is configured to provide forward propulsion whichgenerates lift via the fixed wing.
 7. The hybrid fixed-wing VTOL droneaircraft of claim 5, wherein the electric VTOL propulsion systemcomprises one or more electric motors mechanically coupled to one ormore rotary wings configured to generate lift.
 8. The hybrid fixed-wingVTOL drone aircraft of claim 5, wherein the drone aircraft is configuredto disengage the electric VTOL propulsion system when the internalcombustion propulsion system is engaged and engage the electric VTOLpropulsion system when the internal combustion propulsion system isdisengaged.
 9. The hybrid fixed-wing VTOL drone aircraft of claim 5,further comprising a power management unit configured to control thecharging of the electric battery.
 10. The hybrid fixed-wing VTOL droneaircraft of claim 5, wherein the internal combustion propulsion systemcomprises a gas engine.